Among all components of mobile phone in a prior art, a subscriber identity module card (SIM card) is considered to be the most important one. The way of reasonably using a SIM card is a key point of a mobile phone application.
Subscriber identity module card is actually a smart card having a large scale of integrated circuits, and the SIM card contains personal information of a Global System for Mobile Communication (GSM) user. Only with the installation of a SIM card, a mobile phone can be used; otherwise the mobile phone is only an “idle machine” which allows users to dial emergency calls such as the number 112 provided by telecommunication companies. If a SIM card is inserted into any GSM mobile phone, a phone call can be dialed, and the telephone fee will be billed to the cardholder automatically without the concern of which mobile phone is used to make the call. The SIM card is means of the encryption technology, which is used to store user's data, authentication software and authentication key for the Global System for Mobile Communication phone to identify a user. In the meantime, a user can use the SIM card for the connection and information exchange with the system.
In general, SIM cards are divided into 4 different types according to the type of data stored:
The first type stores fixed information, and such information is stored into a SIM card by the SIM center before a mobile phone is sold, and this information include International Mobile Subscriber Identity (IMSI), Authentication Key (KI), authentication software, and encryption algorithm, etc.
The second type stores temporary network related data including Local Area Identity (LAI), Temporary Mobile Scriber Identity (TMSI), and a public phone network code for prohibiting a connection.
The third type stores business related code including personal identification number (PIN), Personal Unblocking Key (PUK), and charge rate, etc.
The fourth type stores a telephone directory and allows a mobile phone user to input phone numbers anytime.
Since the SIM card records the personal information and data related to the mobile phone user, a mobile phone can carry out the authentication and encryption according to these information and data. If a user moves to a new area to dial or receive a call, the calling exchanger requires an authentication to confirm whether or not the user is an authorized user. Then, the SIM card and the calling exchange simultaneously use an authentication algorithm for computing the authentication key and an 8-digit bundled number. The SIM card is authenticated if the computing results are the same, otherwise the SIM card is rejected, and the user cannot make a call. Further, the use of the SIM card can effectively prevent unauthorized use or wiretap of the call. To protect a mobile phone from an unauthorized use, each SIM card can have a password (PIN code) set by users.
Further, the present Personal Handy-phone System (PHS) mobile phone does not adopt the technology of separating the SIM card and the mobile phone, but it directly uses a private system coding program to write a private system identification (PSID) into the memory of a PHS mobile phone, and such process of writing the PSID into the memory of a PHS mobile phone is generally called “Writing Code” because the technology has a lower entry. The process of obtaining the PSID by the private system coding program is generally called “Reading Code” or a private system coding program is used to remove the PSID which is generally called “Removing Code”, so that the telephone number of the PHS mobile phone can be reinstalled. If a user's mobile phone is stolen or lost, other people can then own and use the mobile phone after the code is “written” and “read”, and thus damaging the rights of the PHS mobile phone user.
If a GSM mobile phone is stolen or lost and the application of stopping the use of SIM card is not filed yet, then others can directly use the stolen mobile phone, and the user has to pay a large amount of telephone bill. After the SIM card is changed, the GSM mobile phone can also be used. Alternatively, the mobile phone is sold as a second-hand item. Any person who has the stolen or missing PHS mobile phone can “remove code” and sell the stolen or lost PHS mobile phone, or owns it after removing code and then writing code. Therefore, regardless of the system of the mobile phone, it is not easy to recover a stolen or lost mobile phone and cannot effectively prevent unauthorized use of the stolen or lost phone.